RE: [EXTERNAL] Re: [PATCH v1 RESEND] SoundWire: Allow Prepare command for Simplified_CP_SM

[Holalu Yogendra, Niranjan]

Apologies for the late response. 
> On 2/10/26 22:34 Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxx> wrote:
> Subject: Re: [PATCH v1 RESEND] SoundWire: Allow Prepare command for Simplified_CP_SM
> 
> On 2/10/26 12: 08, Holalu Yogendra, Niranjan wrote: >> On 2/9/26 20: 13,
> Pierre-Louis Bossart <pierre-louis. bossart@ linux. dev> wrote: 
> On 2/10/26 12:08, Holalu Yogendra, Niranjan wrote:
> >> On 2/9/26 20:13, Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxx> wrote:
> >> On 2/9/26 08: 09, Niranjan H Y wrote:

> Are you referring to the DPN_IntStat::PortReady bit? IOW do the errors during
> prepare happen because the interrupt is not generated?
> If that is the case, then you should be aware of the thread "soundwire:
> stream: Prepare ports in parallel to reduce stream start latency", where it was
> agreed that the use of the PortReady interrupt is broken. We do need to move
> to a different code where we have a polling loop on the
> DPN_PrepareStatus::NotFinished bits.

Thanks for the info.

> So is the problem in the interrupt generation, or is the problem with the 'Not
> Finished' bits?
Both, while using Full CP_SM on a simplified CP_SM device:
* First problem: the interrupt will not get generated on a simple CP_SM device.
* Second problem: even after timeout waiting for interrupt with huge delays,
  we can't rely on 'Not Finished' bits, causing timeout errors.
  In the current code for full CP_SM, 'Not Finished' = 0 is a good response even
  with timeout.

> If that works then an alternate solution to this patch would be to quirk all TI
> devices to use the regular state machine, and use the polling loop as
> suggested by Richard Fitzgerald.
> I think it's worth exploring what happens if the PortReady interrupt is not
> used. If that's broken as well, then your solution would work but needs
> more/better comments indeed.
Currently, we have one device which needs this workaround.
Initially, it looked like a generic solution to me. However, if it makes sense,
I can implement sdw_slave_ops->port_prep to make custom changes
for the required devices only, handle any errors and drop this patch.
Please suggest.

Regards
Niranjan